diff --git a/build/moz.configure/memory.configure b/build/moz.configure/memory.configure
index 262714e261..75f283084a 100644
--- a/build/moz.configure/memory.configure
+++ b/build/moz.configure/memory.configure
@@ -16,19 +16,8 @@ option('--enable-jemalloc', env='MOZ_MEMORY',
 def jemalloc(value, target, build_project, c_compiler):
     if value.origin != 'default':
         return bool(value) or None
-
-    if build_project == 'js':
-        return True
-
-    if target.kernel == 'Darwin' and target.cpu == 'x86_64':
-        # Don't enable by default on 32-bits OSX. See bug 702250.
-        return True
-
-    if target.kernel == 'WINNT' and c_compiler.type in ('msvc', 'clang-cl'):
-        return True
-
-    if target.kernel == 'Linux':
-        return True
+    # Default to the compiler/CRT allocator unless explicitly requested.
+    return None
 
 
 set_config('MOZ_MEMORY', jemalloc)
@@ -77,13 +66,11 @@ option('--enable-replace-malloc',
 
 @depends('--enable-replace-malloc', jemalloc, milestone, build_project)
 def replace_malloc(value, jemalloc, milestone, build_project):
-    # Enable on central for the debugging opportunities it adds.
     if value and not jemalloc:
         die('--enable-replace-malloc requires --enable-jemalloc')
     if value.origin != 'default':
         return bool(value) or None
-    if milestone.is_nightly and jemalloc and build_project != 'js':
-        return True
+    return None
 
 set_config('MOZ_REPLACE_MALLOC', replace_malloc)
 set_define('MOZ_REPLACE_MALLOC', replace_malloc)
diff --git a/js/src/old-configure.in b/js/src/old-configure.in
index e1739af4de..7329fc470d 100644
--- a/js/src/old-configure.in
+++ b/js/src/old-configure.in
@@ -1035,8 +1035,8 @@ WINNT|Darwin|Android)
   ;;
 *)
   if test -z "$GNU_CC"; then
-    STL_FLAGS="-I${DIST}/stl_wrappers"
-    WRAP_STL_INCLUDES=1
+        STL_FLAGS=
+        WRAP_STL_INCLUDES=
   fi
   ;;
 esac
diff --git a/old-configure.in b/old-configure.in
index 1c1d212f9a..a57bc7f5b9 100644
--- a/old-configure.in
+++ b/old-configure.in
@@ -276,8 +276,8 @@ case "$target" in
 
         unset _MSVC_VER_FILTER
 
-        WRAP_STL_INCLUDES=1
-        STL_FLAGS="-I${DIST}/stl_wrappers"
+        WRAP_STL_INCLUDES=
+        STL_FLAGS=
         CFLAGS="$CFLAGS -D_HAS_EXCEPTIONS=0"
         CXXFLAGS="$CXXFLAGS -D_HAS_EXCEPTIONS=0"
     else
@@ -1231,8 +1231,8 @@ Darwin)
   ;;
 *)
   if test -z "$GNU_CC"; then
-    STL_FLAGS="-I${DIST}/stl_wrappers"
-    WRAP_STL_INCLUDES=1
+        STL_FLAGS=
+        WRAP_STL_INCLUDES=
   fi
   ;;
 esac